As shown in FIG. 3, a conventional steam inhaler 41 typically comprises a case 42, an inhalation liquid tank 43, a water tank 45, a steam nozzle 46 and a heater 47. The inhalation tank 43 is detachably received in the case 42 to accommodate inhalation liquid F therein. An inhalation liquid tube 44a extends downwardly into the inhalation liquid tank 43. The upper end of the inhalation tube 44a is formed into an inhalation liquid nozzle 44. The steam nozzle 46 is attached to the inhalation liquid nozzle 44 so as to oppose the latter. The steam nozzle 46 is connected to an upper part of the water tank 45, whose bottom wall adjoins the heater 47 so that the water W in the water tank 45 may be heated. Numeral 48 denotes the cap of the water tank 45.
When electric current is supplied through the heater 47 causing it to be heated up, the water W in the water tank 45 is heated and turns into steam V. The steam V is discharged from the steam nozzle 46, and, owing to Bernoulli's principle, draws up the inhalation liquid F causing it to be discharged from the inhalation liquid nozzle 44. A mixture of the steam V and the inhalation liquid F is thus sprayed from the outlet 42a of the case 42.
In this conventional inhaler 41, the quantity of the water W contained in the water tank 45 is typically 30 to 70 milliliters, and two to three minutes is required before steam V is produced after starting the supply of electric current to the heater 47. If excessive amount of water is contained in the water tank 45, there is a chance that the water in the water tank 45 may be discharged from the steam nozzle 46 in liquid state.
If any water is still left in the water tank 45 when the power to the heater 47 is turned off, a considerable time interval may be required before the spraying stops, thereby causing a significant inconvenience to the user as well as some waste in the inhalation liquid.